A number of conditions leading to neovascularization from the retina ischemia. Of these disorders, diabetic retinopathy is the most prevalent and has become the leading cause of newly diagnosed cases of blindness. It has been suggested (Patz et al, 1977; Brem et al 1977) that the vitreous contains antiangiogenic factors which may control neovascularization of the retina and vitreous. Using an in vitro assay of angiogenesis, namely the proliferation of vascular endothelial cells, we will examine for the presence of angiogenic and/or antiangiogenic factors in the vitreous of normal and diabetic patients. Since the liquifaction of the vitreous in diabetics may result in degraded products which are then angiogenic or chemotactic to vascular endothelial cells, chemotactic ability of the vitreous will be determined. Furthermore, the diabetic vitreous will be studied to determine the physical state of collagen and hyaluoric acid as compared to normal vitreous. There experiments should provide information relevant to the role of the vitreous in retinal neovascularization and elucidate the changes which the vitreous and inner limiting membrane of the retina undergo in diabetic retinopathy.